Dispersion of cross-linkable acrylic resin with amino-aldehyde

ABSTRACT

Heat-hardenable coating compositions comprising a mixture of water-soluble or water-dispersible amine resins with aqueous cross-linking dispersions prepared by emulsion polymerization of a monomer blend as follows: 25-35% BY WEIGHT OF BUTYLMETHACRYLATE 10-25% BY WEIGHT OF ETHYLHEXYLACRYLATE AND/OR N-BUTYLACRYLATE 10-20% BY WEIGHT METHYLMETHACRYLATE 10-20% BY WEIGHT STYROL 1-3% BY WEIGHT METHACRYLIC ACID AND/OR ACRYLIC ACID 10-25% BY WEIGHT POLYPROPYLENE GLYCOL MONOMETHACRYLATE AND/OR POLYETHYLENE GLYCOL MONOMETHACRYLATE IS DESCRIBED. The heat-hardenable coating compositions when employed as metal finishes have excellent weather resistance, flexibility, scratch resistance, adhesion, and freeness from craters.

United States Patent [1 1 Tiimmler etal.

[ July 22, 1975 1 1 DISPERSION OF CROSS-LINKABLE ACRYLIC RESIN WITH AMINO-ALDEHYDE [75] Inventors: Peter Tiimmler; Herbert Zima, both of Graz, Austria [73] Assignee: Vianova-Kunstharz A.G., Vienna,

Austria A 221 Filed: July 2, 1974 211 Appl. No.: 485,273

[30] Foreign Application Priority Data July 3, 1973 Austria 5863/73 July 3, 1973 Austria 5864/73 [52] U.S. Cl.260/29.4 UA; 117/132 BF; 260/291 R;

260/296 TA; 260/3l.4 R; 260/4214; 260/8075; 260/855 [51] Int. Cl. C08f 15/40; C08g 37/32 [58] Field of Search...260/80.75, 29.4 UA, 29.6 TA, 260/855 [56] References Cited UNITED STATES PATENTS 3,082,184 3/1963 Falgiatore et al 260/8075 3,312,654 4/1967 Pratt et al. 260/8075 3,453,346 7/1969 Mabrey et a1 260/8075 3,475,366 10/1969 Borovicka et a1 260/8075 3,657,001 3,669,942 6/1972 Westrenen et al 260/8075 3,787,340 1/1974 Labana et al. 260/8075 Primary Examiner-Murray Tillman Assistant E.taminerArthur H. Koeckert Attorney, Agent, or Firm-A. W. Breiner [57] ABSTRACT 10-25% by weight polypropylene glycol monomethacrylate and/or polyethylene glycol monomethacrylate is described. The heat-hardenable coating compositions when employed as metal finishes have excellent weather resistance, flexibility, scratch resistance, adhesion, and freeness from craters.

8 Claims, No Drawings 4/1972 Parker 260/8075 DISPERSION F CROSS-LINKABLE ACRYLIC RESIN WITH AMINO-ALDEI-IYDE The present invention is directed to heat-hardenable coating compositions comprising mixtures of watersoluble or water-dispersible amine resins with aqueous polymer dispersions which will undergo cross-linking. The binders can be used to particular advantage in metal finishes.

According to conclusions and opinions set forth in the protective coating art, the advantages of aqueous dispersions, such as low viscosity combined with high solids; high molecular weight; no volatile toxic components, etc., are offset to a substantial degree by serious disadvantages of such systems, including swelling due to the water of the coatings, thereby reducing weather resistance, high porosity, low scratch resistance, and cratering on spray application. To find a solution to these disadvantages, specific polymer systems are described. Various prior art references describe heatcurable coating compositions which contain as the main binder or sole binder aqueous dispersions of copolymers of acrylic monomers with co-polymerizable compounds. German Offenlegungsschrift No. 1,519,307 teaches aqueous alkaline polymer dispersions containing, in addition, aqueous aminoplasts, a coalescing agent, and a tertiary amine. The polymer dispersions are a blend of two co-polymers, one of them being based on (methylolated) (meth)acrylamide. German Auslegeschrift No. 1,269,337, and German Offenlegungsschrift Nos. 1,794,223 and 1,669,133 describe self-curing co-polymer dispersions based on N-methylolacrylamide or similar substances. German Auslegeschrift No. 1,248,194 describes copolymer dispersions cross-linking with amineformaldehyde or phenol-formaldehyde condensation products, the main monomers being a,B-unsaturated carboxylic acid nitriles. In general, the aforesaid dispersions are not suitable for high quality metal finishes, e.g., automobile finishes, since they do not meet the requirements with respect to surface hardness, nonyellowing, high gloss, good gloss retention, and particularly flexibility and adhesion.

German Offenlegungsschrift No. 2,252,065 describes dispersions for metal finishes which contain two nitrogen-free monomer units, one of them being an unsaturated polyester with terminal hydroxy groups. According to this reference, use of such dispersions allows improvements in gloss as well as scratch resistance; however, the flexibility is only sufficient as a maximum, meaning that the practical use of the products is nearly ruled out.

According to the present invention, it has been found that polymer dispersions requiring a selection of specific monomers and specific weight ratios thereof provide coating compositions useful as high-quality stoving paints, which, in mixture with water-soluble or waterdispersible amine resins, yield films with excellent performance in terms of flexibility, scratch resistance, weather resistance, and freeness from craters. The coating compositions of the invention are characterized in that they comprise a blend of l. 60 95 by weight of apolymer dispersion prepared by emulsion polymerization, in known manner, of

25 35 by weight of n-butylmethacrylate 10 25 by weight of ethylhexylacrylate and/or nbutylacrylate l0 20 by weight of methylmethacrylate l0 20 by weight of styrol l 3 by weight of methacrylic acid and/or acrylic acid 10 25 by weight of polypropyleneglycol monomethacrylate and/or polyethyleneglycol monomethacrylate v 2. 5 40 by weight of a water-soluble and/or water-dispersible amineformaldehyde-condensation product, i.e., a cross-linking component, the methylol groups of which are partially or completely etherified with monoalcohols,

3.0 150 by weight, preferably 0 80 by weight of the total solids of( l and (2) of a pigment paste consisting of a. 4 by weight of a pigment and/or filler, and

b. 30 96 by weight of a pigment wetting agent 4. normal paint additives and/or curing catalysts and- /or neutralizing agents. Paints based on the aforesaid coating compositions yield stoving finishes with outstanding resistance to corrosion, and chemical and mechanical influences.

Deviations from the nature of the mentioned comonomers in the aqueous dispersion, as well as from the quantities thereof, have an adverse influence on the paint performance as well as on the stability of the dispersion. For instance, without a minimum amount of styrol the dispersion cannot be produced free from coagulates and it does not have sufficient stability. The other monomers cannot be substituted for other monomers, or omitted, without detrimental effects on the properties of the co-polymer. The use of polypropylene glycol monomethacrylate or polyethyleneglycol monomethacrylate is of special importance. Other hydroxyesters impart cracking to the drying film, reduce flow and flexibility; whereas the films produced from dispersions of the invention show excellent flexibility, smoothness, flow, and adhesion. ,The given weight ratios, in extreme cases, can be varied upward or downward by a maximum of 5 percent. The specific dispersions are co-polymerized using emulsion polymerization techniques in known manner in the presence of anionic emulsifiers, optionally also non-ionic emulsifiers, and free radical initiators. Suitable anionic emulsifiers for use in preparing the co-polymers are hydrocarbon sulfonates, such as dodecylbenzolsulfonate, sodium laurylsulfate, sodium tridecylsulfate, or the sulfates or ethoxylated fatty alcohols, like-sodium lauryl ethoxylate sulfate, or an octylphenol reacted with 2 mols ethylene oxide and sulfated. It is advantageous to co employ non-ionic emulsifiers of the type of ethoxylated alkyl phenols together with the anionic emulsifiers.

Suitable amine-formaldehyde condensates are watersoluble, or at least water-dispersible amineformaldehyde condensates normally used in the paint industry, based on the aminotriazines, such as melamine, the benzoguanamine, etc., as well as urea, or similar substances. The substantially or completely etherified types, either as monomers or oligomers, are preferred, e.g., hexamethoxymethylmelamine.

Suitable pigments or fillers are those normally used by the paint industry. The quantities required for the various end uses and colors are known to those skilled in the art. Suitable pigment wetting agents can be chosen from a variety of groups including 1. water-dilutable solution polymers of the acrylic type, either available on the market or produced in known manner. Those polymers are preferred which are formed from monomers similar to those of the binder dispersion, the proportion of (meth)acrylic acid being increased to provide sufficient solubility in water.

2. Acrylic resin dispersions produced according to the process of the invention, with percent or more (meth)acrylic acid, and a reduced content of polypropylene or polyethyleneglycolmonomethacrylate.

3. Solutions of anionic and/or non-ionic emulsifiers in high-boiling watertolerant solvents, e.g., 2- dimethyl-4-oxymethyl-1,3-dioxolane, ethyleneglycolmonobutyletheracetate, ethylene glycolmonoethyl ether acetate, ethylene glycolmonoethyl ether. The pigments, together with the pigment wetting agent, are dispersed with normal grinding equipment and are blended with the dispersion. (1) and (2) above are ideally suited for preparing stable pigment pastes with inorganic pigments.

The following preparations and examples illustrate the invention without limiting the scope thereof. Parts are by weight.

EXAMPLE 1 In a polymerization reaction vessel a. 2.9 parts dodecylbenzolsulfonate 9.8 parts ethoxylated octylphenol (with 16 mols ethylene oxide) 2 parts ammonium persulfate are dissolved in 1090 parts deionized water. The solution is heated to 75C., and the following blend (b) is continuously added over a period of 90 minutes:

b. 265 parts butylmethacrylate 140 parts ethylhexylacrylate 141 parts methylmethacrylate 141 parts styrol 190 parts propyleneglycolmonomethacrylate parts methacrylic acid 4.4 parts dodecylmercaptan During the addition the temperature is slowly raised to 85C. After the addition, 28 parts of a C C fatty alcohol reacted with 25 mols ethylene oxide and 3 parts of an octylphenol which was reacted with 3 mols ethylene oxide and subsequently sulfated, dissolved in 100 parts water, are added. To complete conversion, the temperature is raised to 95C., and held for 10 minutes. After cooling, a highly stable dispersion with about 44 percent solids is obtained.

For further processing the pH-value of the dispersion is adjusted to 7.5 with an alkanol amine, e.g., dimethylethanolamine.

EXAMPLE 2 Analogous to Example 1, a polymer dispersion is pro duced using the following blend (b):

b. 265 parts butylmethacrylate 126 parts n-butylacrylate 155 parts methylmethacrylate 141 parts styrol 190 parts polypropyleneglycolmonomethacrylate 15 parts methacrylic acid 4.4 parts tert.dodecylmercaptan EXAMPLE 3 Analogous to Example 1, a polymer dispersion is prepared using the following blends (a) and (b):

a. 3 parts sodiumlaurylethoxylatesulfate 9.8 parts ethoxylated octylphenol (with 16 mols ethylene oxide) 2 parts ammoniumpersulfate 1090 parts deionized water b. 225 parts butylmethacrylate 225 parts ethylhexylacrylate 162 parts methylmethacrylate 180 parts styrol 90 parts polypropyleneglycol monomethacrylate 18 parts acrylic acid 4.4 parts tert.dodecylmercaptan EXAMPLE 4 Analogous to Example 1, the following blends (a) and (b) are polymerized:

a. 3.0 parts of an octylphenol reacted with 2 mols ethylene oxide and subsequently sulfated 9.8 parts of an ethoxylated octylphenol (with 16 mols ethylene oxide) 2 parts ammoniumpersulfate 1090 parts deionized water b. 320 parts butylmethacrylate 90 parts ethylhexylacrylate 90 parts methylmethacrylate 180 parts styrol 180 parts polypropyleneglycolmonomethacrylate 30 parts methacrylic acid 4.4 parts tert.dodecylmercaptan The polypropylene glycolmonomethacrylate can be replaced by the same quantity of polyethylene glycol monomethacrylate. The obtained results are comparable.

The preparation of pigment pastes for use in paint compositions demonstrating this invention is shown in Table I hereinafter.

1 148.5 pans acrylic resin/% 237.5 parts butylglycolacetate 1 1.0 parts dimethylethanolamine 11 161 parts acrylic resin/60% 225 parts ethylglycol 10 parts dimethylethanolamine' 111 As in 1 1V As in 1 V 350 parts acrylic dispersion 28 in water V1 744 parts 2-dimethyl-4-oximethyl- 1,3-dioxalane 12.8 parts dodecylbenzylsulfonate 12.8 parts ethoxylated cetyl alcohol (25 ethylene oxide) ball mill with steatite balls (15 hours) 386 parts Tio -rutile 386 parts molybdatered As in I (10 hours) 58 parts pigment blue As in l (60 hours) 15 No. 74160 58 parts carbon black As in 1 hours) 392 parts molybdatered As in l (10 hours) 200 parts molybdatered three roll TABLE l-Continited Preparation of Pigment Paste Eum- Pigment of Wetting Agent Pigment Mill Type V11 As in /'i 200 parts TiO -rutilc As in V1 Vlll As in V1 50 parts pigment blue As in VI No. 74160 [X 170 parts acrylic resin" 56.7% in 386 parts TiO -rutile As in 1 (15 hours) butylglycolacctate 216 parts butylglycolacetate l 1 parts dimethylethanolamine Acrylic resin ""is a self-reacting water-soluble acrylic polymer prepared according to Austrian Patent Specification No. 291.571; acrylic resin ""is a self-reacting water-soluble acrylic polymer on the basis of methylolated ucrylamide; acrylic resin "is a water-soluble acrylic polymer on the basis of the monomers blend of Example 1. with 9 7r methacrylic acid and 12 percent polypropylene glycolmonomethacrylatel monocthyleneglycolmonobutylether acetate ""monoethyleneglycol monoethyl ether salt formation for obtaining solubility in water according to Color Index dispersion according to Example 1 with 9 percent methacrylic acid and 12 percent polypropylene g1yeolmonomethaerylate For tinting the paints pigmented with organic pigments. available pigment preparations in form olpastes for aqueous media (e.g.. Colan\'l" or 'leig-P-Pigmente) can also he used Paint preparations based on this invention, and the mine, the amine resin solution, a curing catalyst and pigment pastes of Table l are set forth in Table 11 herewater such that an end viscosity of about s DIN 53 inafter. 211 is obtained.

TABLE 11 Preparations l Pigment Paste t 33.2 33.2 33,3 33 3 Pigment Paste lI 33.2 Pigment Paste 111 1O Pigment Paste 1V Pigment Paste V 30.3 Pigment Paste V1 Pigment Paste V11 Pigment Paste V111 Pigment Paste 1X 332 Acrylic dispersion, 43.2%

of Example 1 65 65 60 65 74 74 74 (,3 Acrylic dispersion, 44%

of Example 2 Acrylic dispersion. 41.5%

of Example 3 Acrylic dispersion, 45

of Example 4 4 4 hexamethoxymethylmelamine, 100% 8 8 8 8 8 8 8 8 8 8 8 8 water 11 13 12 l2 14 12 11 12 12 l3 l4 8 p-toluol sulfonic acid 10%, in water 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6

Hexamethoxymethylmelamine can optionally be dissolved in suitable solvents in order to render more handleable the crystalline types. Amounts are parts by weight. %,where indicatedjs Z. solids. or non-volatile.

1n preparations 1 12 of Table 11, the paints are pre- The various paints prepared according to Table 11 pared as follows: were evaluated, the results tabulated in Tables Ill and 50 1V hereinafter. Table IV is data on corrosion tests. Un- With constant stirring the pigment paste is blended less otherwise stated. the paints are sprayed onto clean with the aqueous acrylic dispersions of the invention; untreated steelpanels (0.8 mm) and stoved for minneutralized to a pH-value of 7.5 with dimethylethanolautes at 160C.

TABLE 111 2 3 4 5 6 7 8 9 1O ll 12 film thickness/pm 38 40 36 40 41 39 38 40 45 40 42 Erichsen indentation 7.4 7.2 7.5 7.9 8.1 7.8 7.9 8.1 7.6 7.8 7.4 7.6 crosshatch DIN 53 151 1-2 1-2 1-2 1 l-2 1-2 1-2 1 2-3 2 1-2 2 impact 65 7O 75 75 75 8O 8O 75 70 7O gloss (Goni0- photometer GP 2/45) 79 8O 81 77 85 81 79 81 89 85 79 81 endulum hardness DIN 53157, Konig 151 156 162 156 145 165 139 102 142 151 145 mandrel ASTM D 522 41 32 32 32 32 32 32 32 32 32 32 32 32 xylol test TABLE Ill Conlinued 2 3 4 S 6 7 8 9 10 ll 12 (xylol soaked cotton pad) after 4 minutes U-l U-l U-l U-l Ul Ul U-l U-l U-l U-l U-l U-l The evaluated paint films were sprayed onto untreated steel panels of 0.8 mm thickness and cured at 160C. for 30 minutes. Gardner impact, inch pounds. Gloss with goniophotometer GP at 45gloss 2:32: fg zfgz Xylol test: U: no attack after indicated time. film not swollen, cannot be scratched off with fingernail. l slightly swollen after indicated time. can be scratched off with some effort. 2 slightly swollen after indicated time, can be scratched off easilyv 3 strongly swollen after indicated time. film crinkles and starts to peel off. 4 film almost dissolved, tacky, can be wiped off.

TABLE IV tropical test 500 hours mlgl mlgl mlgl mlgl mlgl mlgl mlgl mlgl m3g2 m2gl mlgl m2g1 Kesternich corrosion test (0.2 1 S0 no attack m3gl no attack rounds) salt spray resistance ASTM B 117-64 550 hours m2gl m2g1 m2gl m2gl m2gl m2gl m2gl m3g2 m3g2 m2g2 m2gl m2g1 water soak at 40C. 350 hours ml gl m4g2 m2g2 mlgl m2g1 Corrosion tests were run on Zink Bonder No. I panels. with an anti-corrosion primer applied by electrodeposition and wet-sanded with emery wet paper No. 600.

It is claimed: to claim 1 wherein the pigment wetting agent is a 1. Heat hardenable coating compositions comprising water-soluble solution polymer of the acrylic type. 3. Heat hardenable coating compositions according l. 60 95 by weight of a polymer dispersion preto claim 1 wherein the pigment wetting agent is an pared by emulsion polymerization of aqueous dispersion of acrylic monomers. 25 35 by weight of butylmethacrylate 4. Heat hardenable coating compositions according 1O 25 by weight of ethylhexylacrylate and/or to claim 1 wherein the pigment wetting agent is a solun-butylacrylate tion of an anionic emulsifier in high-boiling water- 10 2O by weight of methylmethacrylate tolerant solvents. l0 2O by weight of styrol 4O 5. Heat hardenable coating compositions according l 3 by weight of methacrylic acid and/or to claim 1 wherein the pigment wetting agent is a soluacrylic acid tion of a non-ionic emulsifier in high-boiling water- 10 25 by weight of polypropyleneglycol monotolerant solvents.

methacrylate and/or polyethyleneglycol mono- 6. Heat hardenable coating compositions according methacrylate, to claim 1 wherein the pigment wetting agent is a solu- 2. 5 4O by weight of a water-soluble or watertion of an admixture of anionic and non-ionic emulsifidispersible amine-formaldehyde-condensation ers in high-boiling water-tolerant solvents. product, the methylol groups of which are partially 7. Heat hardenable coating compositions according to claim 1 wherein the polymer dispersion is prepared in the presence of anionic emulsifiers.

or completely etherified with monoalcohols, and 3. O 150 by weight of the total solids of l) and (2) of a pigment paste of 8. Heat hardenable coating compositions according 4 70 by weight Ofa pigment and/0r finer and to claim 1 wherein the polymer dispersion is prepared b, 30 96 by weightof a pigmentwetting agent. in the presence of anionic and non-ionic emulsifiers. 2. Heat hardenable coating compositions according 

1. HEAT HARDENABLE COATING COMPOSITIONS COMPRISING 1.60 - 95 % BY WEIGHT OF A POLYMER DISPERSION PREPARED BY EMULSION POLYMERIZATION OF 25 - 35 % BY WEIGHT OF BUTYLMETHACRYLATE 10 - 25 % BY EIGHT OF ETHYLHEXYLACRYLATE AND/OR NBUTYLACRYLATE 10 - 20 % BY WEIGHT OF METHYLMETHACRYLATE 10 - 20 % BY WEIGHT OF STROL 1 - 3 % BY WEIGHT OF METHACRYLIC ACID AND/OR ACRYLIC ACID 10 - 25 % BY WEIGHT OF POLYPROPYLENEGLYCOL MONOMETHACRYLATE AND/OR POLYETHYLENEGLYCOL MONOMETHACRYLATE,
 2. 5 - 40 % BY WEIGHT OF A WATER-SOLUBLE OF WATER-DISPERSIBLE AMINE-FORMALDEHYDE-CONDENSATION PRODUCT, THE METHYLOL GROUPS OF WHICH ARE PARTIALLY OR COMPLETELY ETHERIFIED WITH MONOALCOHOLS, AND
 3. 0 - 150 % BY WEIGHT OF THE TOTAL SOLIDS OF (1) AND (2) OF A PIGMENT PASE OF A. 4 - 70 % BY WEIGHT OF A PIGMENT AND/OR FILLER, AND B. 30 - 96 % BY WEIGHT OF A PIGMENT WETTING AGENT.
 2. 5 - 40 % by weight of a water-soluble or water-dispersible amine-formaldehyde-condensation product, the methylol groups of which are partially or completely etherified with monoalcohols, and
 2. Heat hardenable coating compositions according to claim 1 wherein the pigment wetting agent is a water-soluble solution polymer of the acrylic type.
 3. Heat hardenable coating compositions according to claim 1 wherein the pigment wetting agent is an aqueous dispersion of acrylic monomers.
 3. 0 - 150 % by weight of the total solids of (1) and (2) of a pigment paste of -a. 4 - 70 % by weight of a pigment and/or filler, and b. 30 - 96 % by weight of a pigment wetting agent.
 4. Heat hardenable coating compositions according to claim 1 wherein the pigment wetting agent is a solution of an anionic emulsifier in high-boiling water-tolerant solvents.
 5. Heat hardenable coating compositions according to claim 1 wherein the pigment wetting agent is a solution of a non-ionic emulsifier in high-boiling water-tolerant solvents.
 6. Heat hardenable coating compositions according to claim 1 wherein the pigment wetting agent is a solution of an admixture of anionic and non-ionic emulsifiers in high-boiling water-tolerant solvents.
 7. Heat hardenable coating compositions according to claim 1 wherein the polymer dispersion is prepared in the presence of anionic emulsifiers.
 8. Heat hardenable coating compositions according to claim 1 wherein the polymer dispersion is prepared in the presence of anionic and non-ionic emulsifiers. 